I need to know whether to invest in a new lighter axel for a go kart Before I take the plunge, I'd like to get "some" kind of idea of the kinds of gains one can expect from this kind of change. The conditions as I know Them. the 5Hp engine achieves max torque at 5200-5400 RPM. the motor is geared at 6:1 and the gearing from the motor to the rear axel is 34/27.. for a combined gear ratio of 4.76:1. The current rear axel weighs on the order of 4 Lbs, without tires. what kind of RPM gains could one expect from reducing real axel weight to 2 lbs? Note: the different between first and last is somewhere on the order of 1-2 % of rear axel RPM.